IQ Technologies

Two Cost-Effective Applications for Intensive Quenching of Steel Parts

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OCThe Intensive Quench (IQ) process is an alternative way of quenching steel. It involves a very rapid and uniform cooling of steel products in water with cooling rates several times greater than that of conventional quenching in agitated oil or polymer. Through this interesting article, explore the unique method and its use in the automotive industry.

This article first appeared in Heat Treat Today’s August 2021 Automotive print edition Edward Rylicki, vice president of Technology, and Chris Pedder, technical manager of Heat Treat Products and Services, at Ajax TOCCO Magnethermic Corp., as well as Michael Aronov, CEO of IQ Technologies, Inc.

Introduction

The Intensive Quench (IQ) process is an alternative way of quenching steel parts that originated with Dr. Nikolai Kobasko of Ukraine in 1964.1 It involves a very rapid and uniform cooling of steel products in water with cooling rates several times greater than that of conventional quenching in agitated oil or polymer. The IQ process is interrupted at an optimal time when the surface compressive stresses reach their maximum value, and the part-hardened layer reaches its optimal depth. A proprietary computer program is used for determining an optimal dwell time for steel parts of different shapes and dimensions.

Ajax TOCCO Magnethermic Corporation has recently acquired assets of IQ Technologies, Inc. of Cleveland, Ohio. Over the last 20 years, IQ Technologies has been commercializing an intensive quenching (IQ) process for steel parts in the U.S. and overseas.

Figure 1. IQ system for processing gun barrels and long shafts

The IQ process is conducted in IQ water tanks (a batch IQ technique) and in single-part processing high-velocity water flow IQ units when parts are quenched one at a time. Steel parts are austenitized prior to intensive quenching in heat treating furnaces or using an induction through heating (ITH) method.2 As an example, Figures 1 and 2 present two production IQ systems. Each includes a single-part processing high-velocity water flow unit built by IQ Technologies. The IQ unit in Figure 1 is equipped with a single-shot low frequency ITH station built by Ajax TOCCO Magnethermic. It is designed for processing gun barrels and shafts of up to 36” long and up to 2” in diameter. The IQ unit in Figure 2 is equipped with a box atmosphere furnace and is designed for processing gear products of up to 8” in diameter and shafts of up to 15” long.

Figure 2. IQ system for processing gear products and shafts installed at Euclid Heat Treating Co.

Coupling of the single-part processing IQ technique with the ITH method (ITH + IQ) is the most effective way of IQ process implementation. It allows conducting of heat treating operations within a manufacturing cell in line with a steel parts production process. This paper focuses on two applications of the ITH + IQ process:

  1. Elimination of a costly, energy and time-consuming carburization process
  2. Substitution of a one-step ITH + IQ process for a two-step heat treatment consisting of batch quenching parts in oil or polymer for part core hardening followed by induction hardening

Elimination of Carburizing Process

The carburizing process is the most expensive and time-consuming heat treatment process. Elimination of the carburizing process by implementing the IQ method requires the use of limited hardenability (LH) steels. LH steels are medium to high carbon steels having exceptionally low content of alloy elements. When quenched intensively, LH steels provide a hard, martensitic case, tough, ductile core, and high residual surface compressive stress mimicking a carburized condition without carburization.

Figure 3. Side pinion

Two IQ case studies were conducted with two major U.S. automotive parts suppliers for evaluating the IQ process when applied to side pinions and drive pinions made of LH steel. Results obtained were compared to the same parts made of alloy steel, carburized and quenched in oil.

Side Pinions

Figure 3 presents a picture of the evaluated side pinion having the outside diameter (OD) of 80mm and inside diameter (ID) of 27mm. Standard pinions were made of alloy 8620 steel, carburized, quenched in oil, and shot peened. Pinions made of LH steel (acquired from Russia) were quenched intensively in the high-velocity water flow single-part processing IQ unit. The LH steel pinions were not shot peened after heat treatment. A chemical composition of the LH steel used is presented in Table 1.

To evaluate the side pinion structural and stress conditions during heat treatment, DANTE computer simulations were conducted by DANTE Solutions, Inc. of Cleveland, Ohio, for standard carburized side pinions and for intensively quenched pinions made of LH steel.3 It was shown that the microstructure of the carburized and quenched-in-oil side pinion consists of martensite formed within the part carburized case and bainite in the remaining part cross section (Figure 4).

Figure 4. Microstructure distribution

Figure 5. Minimum principal stress

A microstructure distribution in the intensively quenched side pinion made of LH steel consists of a martensitic structure in the part surface layer, a bainitic structure beneath the martensitic case, and a perlitic structure in the part core. The martensitic case is generally deeper in the intensively quenched LH steel pinion compared to that of the standard pinion.

Figure 5 presents calculated values of the minimum principal stress that represent residual surface compressive stresses. As seen from the figure, the intensively quenched LH steel side pinion has residual surface compressive stresses greater than that of the carburized side pinion quenched in oil.

Figure 6. Experimental microhardness data for LH steel side pinion (PL – pitch line, RR – tooth root, TOT – tooth tip)

Figures 6–8 present experimental data obtained by the customer for the intensively quenched side pinions made of LH steel. Figure 6 shows hardness profiles at the pinion pitch line, tooth root, and tooth tip. Figure 7 presents an etched pinion tooth sample showing a martensitic case. As seen from the above figures, the IQ process provided the hard case and the ductile core that mimics a hardness distribution after carburizing.

Figure 7. Hardened case in intensively quenched side pinion made of LH steel

Figure 8 shows a residual surface compressive stress distribution for the LH steel side pinion root area. Residual surface compressive stresses for the intensively quenched side pinion made of LH steel were greater than that of the standard carburized and shot peened pinion. Fatigue testing has proven that intensively quenched side pinions made of LH steel have a longer service life compared to the standard pinions.

Figure 8. Residual stress distribution in intensively quenched side pinion made of LH steel

Drive Pinions

An IQ case study was conducted for drive pinions with one of the major U.S. automotive parts suppliers. Drive pinions were made of LH steel produced by a U.S. steel mill (the LH steel chemistry is proprietary information). Figure 9 presents a picture of the evaluated drive pinion. The drive pinions were quenched in the high-velocity water flow single-part processing IQ unit. Per customer evaluation, the hardness profile in the intensively quenched drive pinions made of LH steel mimics the hardness distribution in the standard carburized and oil quenched drive pinions, while the values of the residual surface compressive stresses are greater for the intensively quenched LH steel pinions compared to that of the standard drive pinions. (This information is also not presented in the paper due to its proprietary nature.)

Figure 9. Drive pinion

The intensively quenched drive pinions met all the customer’s metallurgical specifications and passed both the ultimate strength test and the fatigue test. It was shown that the part fatigue resistance improved by about 150% compared to that of standard carburized and quenched in oil drive pinions. In addition, distortion of the intensively quenched drive pinions is so low that no part straightening operations are required.

Application of the ITH + IQ process and LH steels for side pinions and drive gears will result in the following major benefits:

  • Less energy usage due to elimination of the long carburization process
  • Lower overall part costs
  • Cleaner parts and work environment due to use of water instead of quench oil or polymers
  • Lower work-in-process inventories and shortened lead times, due to possibility of running heat treat operations in part manufacturing cell

Substitution of One-Step Heat Treating Process for Two-Step Heat Treatment

A two-step heat-treating process consisting of batch quenching of parts in oil or polymer for core hardening, followed by induction hardening, is used in the industry for many steel products. This heat-treating process provides parts with a hard case and tough, ductile core that is similar to the carburizing process. A substitution of the ITH + IQ method for the two-step heat-treating process is another attractive possibility for steel part makers in reducing the part cost.

Figure 10. Typical input shaft

One of the major U.S. automotive parts suppliers applied this approach to the manufacturing of input shafts (Figure 10). The input shafts are currently made of high-alloy medium-carbon steel that requires annealing after forging. The intensively quenched input shafts were made of plain medium carbon steel that did not require annealing after forging. The shafts were quenched at the Ajax TOCCO Magnethermic Detroit Development & Support Center.

Per customer evaluation, the hardness profile in the intensively quenched input shafts was similar to that of standard shafts. Residual surface compressive stresses in the intensively quenched shafts are greater compared to that of the standard input shafts resulting in longer part fatigue life of up to 300%. (Per the customer’s request, the actual data on the part hardness profile, microstructure distribution, and values of residual surface compressive stresses are not presented in the paper.)

Figures 11 and 12 present current and improved input shaft production flow charts accordingly. As seen, an introduction of the ITH + IQ process allows elimination of the following input shaft manufacturing steps: annealing after forging, batch oil quenching, and shaft straightening. In addition, part shipping and material handling operations will be significantly reduced. In summary, the application of the ITH + IQ process provides the following major benefits in this case:

  • Less energy usage due to the elimination of two heat treating processes: annealing after forging and batch quenching in oil
  • Less material cost due to substitution of plain carbon steel for high alloy steel
  • Lower overall part costs due to the use of less expensive steel, reduction of heat treatment cost, elimination of all expenses associated with the use of quench oil, reduced cost of shipping and material handling, and elimination of part straightening operations
  • Cleaner parts and work environment due to use of water instead of quench oil or polymer
  • Lower work-in-process inventories and shortened lead times, due to possibility of running heat treat operations in part manufacturing cell

Figure 11. Drive pinion current production flow chart

Figure 12. Drive pinion improved production flow chart

Conclusion

Implementation of the ITH + IQ process and the use of LH steels will make possible the conducting of heat treat operations in a steel part manufacturing cell, reducing work-in-process inventories and shortening lead time. At the same time, tremendous energy savings, significant reduction of a carbon footprint, and overall part cost can be achieved due to eliminating the carburizing process and the use of quench oil, and due to the substitution of plain carbon steel for high alloy material. Improved work environment is also a bonus.

IQ Facility at Ajax TOCCO Magnethermic Detroit Development & Support Center

Ajax TOCCO Magnethermic has set up an IQ facility at its Detroit Development & Support Center (Figure 13). The facility includes a single-part processing IQ unit and an induction heating station. The IQ unit is capable of processing gear products, shafts, etc. of up to 8” in diameter and 15” long. The IQ unit controls monitor the following parameters: water temperature, water flow velocity, pump pressure, and dwell time. The induction heating fixture consists of a pneumatic horizontal indexing heat station used for power supply load matching and inductor positioning. The load matching station can be fed by numerous power supplies capable of various operating frequencies and power levels up to 600 kW.

The Detroit Development & Support Center also houses a large area for the manufacture and repair of induction tooling, along with engineers needed for the design of prototype and production tooling. There is also a metallurgical lab with the equipment and staff necessary to support the ITH + IQ process development. The metallurgical lab contains macro and micro hardness testers, cut-off wheels, polishing equipment and a metallograph for analyzing microstructures.

 

References

[1] N.I. Kobasko and N.I. Prokhorenko, “Quenching Cooling Rate Effect on Crack Formation of 45 Steel,” Metalloved. Term. Obrab., Met., No. 2, 1964, p. 53-54 (in Russian).

[2] M.A. Aronov, N.I. Kobasko, J.A. Powell, “Intensive Quenching of Steel Parts,” ASM Handbook, Volume 4A. Steel Heat Treating Fundamentals and Processes, 2013, p. 198-211.

[3] B.L. Ferguson, Zhichao Li, N.I. Kobasko, M.A. Aronov and J.A. Powell, “Limited Hardenability Steels and Intensive Quenching,” Proceedings of ASM Heat Treating Conference, Indianapolis, 2009.

About the Authors: Edward Rylicki is the vice president of Technology and Chris Pedder is the technical manager of Heat Treat Products and Services, at Ajax TOCCO Magnethermic Corp. For more information, contact info@ajaxtocco.com or 800.547.1527

Michael Aronov is the CEO at IQ Technologies, Inc. For more information, contact Michael at m.a.aronov@sbcglobal.com.

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Joe Powell Comments on Marquenching and Austempering

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Last week, we ran a news release about ThermoFusion in California expanding their heat treat capabilities to include marquenching and austempering (click here to see that release). In that short article, some comments were made about the aggressiveness of various quench methods and their effect on distortion and cracking.

Joe Powell, of Akron Steel Treating Company, Integrated Heat Treating Solutions, LLC, IQDI Products, LTD., and IQ Technologies Inc, one of the heat treat industry’s foremost experts on quenching, wrote in to help educate all of us a bit more on the finer points of quenching. Below are his comments. Joe can be reached at JoePowell@akronsteeltreating.com.

 

Doug,

In your recent article, you stated that Marquenching and Austempering use a “less aggressive” quench cooling rate, “and reduce distortion caused by rapid temperature change (thermal shock)” which is only half true.  The main mechanism that allow a molten salt quench to reduce distortion is the elimination of mixed phase cooling – there is no slow film boiling (gas) phase cooling mixed with the high-evaporative cooing phase of nucleate boiling, but only a single phase of all liquid convection cooling.   It’s the non-uniformity of cooling at the surface of the part that will distort or crack the part not so much the rate of cooling.

Joe

Joseph A. Powell, President
Akron Steel Treating Company

Integrated Heat Treating Solutions, LLC
IQDI Products, LTD. 
IQ Technologies Inc

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360 Degree Part Design: Listen to Your Heat Treat Department

/ FEATURED NEWS, MANUFACTURING HEAT TREAT, QUENCHING NEWS

Publisher’s Note: Joe Powell, President of Akron Steel Treating Company and IQ Technologies, raises a very compelling point that part designers should work closely with heat treaters to achieve the lowest possible cost of production. In his introduction, he lists out some lofty goals that were set by an ASM Committee back in 1999…a meeting I was fortunate to attend. The goals were lofty then, and they continue to be lofty now. Mr. Powell offers a road map for getting closer to these goals.

Enjoy the read.

Doug Glenn, Publisher

By Joe Powell, President, Akron Steal Treating & IQ Technologies

 

It’s now 2017, almost 18 years since the ASM R+D committee set forth its Vision 2020, a list of goals for the heat treating industry by the year 2020:

BACKGROUND AND INDUSTRY NEEDS

Industry needs have been determined from the information brought forth by various

committee efforts and surveys over the last five years. Heat treating industry executives identified many of these needs, and prepared a view of the ideal future. This view has been named Vision 2020, and the established performance targets, based in energy, environment, productivity and quality, and industry performance are:

  • Reduce energy consumption by 80%
  • Improve insulation
  • Achieve zero emissions
  • Reduce production costs by 75%
  • Increase furnace life ten-fold
  • Reduce the price of furnaces by 50%
  • Achieve zero distortion and maximum uniformity in heat treated parts
  • Return 25% on assets
  • Create 10-year partnerships with customers.”

It appears our industry has a way to go before meeting the Vision 2020 goals.  Whether you work for a captive heat treating division of a part manufacturer or do heat treating at a commercial heat treating shop for many different part manufacturers, the goals set forth in 1999 are still worth pursuing.

What can we do to speed up the process of achieving these goals?   

The above goals can be summarized as making “better parts” at a total lower cost of manufacture.   Heat treating is a crosscutting technology.  To become more efficient in the heat treating process we must look at not only our heat treating processes, but also look concurrently “upstream” and “downstream” from the heat treating process.  All the parties in the part making value stream must collaborate to eliminate waste in each of their own processes as well as the waste that occurs from the interaction between each process.  Doing the proper processes in the right order is also key to eliminating waste.  For example, create a “near net shape” part before carburizing so the carburize layer that took so long to diffuse into the part is not removed in the post-hardening grinding operation.

[blocktext align=”left”]Heat treating considerations must become part of the design and engineering processes from their inception. Heat treaters must give their input for what material is best for the part application, considering not only the desired part fit and function, but the needed physical and mechanical properties. [/blocktext]

Two of the above goals: “reduce production costs by 75%” and “achieve zero distortion and maximum uniformity in heat treated parts” will require innovations in not only heat treating processes, but also heat treating equipment.   The modeling of the heat treating process must become an integral part of the FEA modeling of the part design.  The designer should focus on fit and function as well as achieving the needed mechanical properties, all at the lowest overall cost of manufacture.   Part design engineers cannot meet these goals employing the same heat treating processes and using the same alloys of material that have been used for the last 100 years.   Innovations in heat treatment must be developed collaboratively, crosscutting the many silos of expertise that are needed for making the part.

Part distortion after heat treatment costs part makers billions of dollars each year in post-heat treat operations.  Achieving predictable part distortion after quenching with optimal grain refinement for a given alloy of steel depends on selecting the proper heat treat methods, e.g., proper racking, uniform heating, uniform atmosphere protection and most importantly the proper quenching process.  However, the selection of the optimal quenching method is only enabled by a coordinated choice of the type of alloy used.  Although higher alloy steel allows the use of gas quenching, air hardening steels usually mean higher cost.  In addition, a higher hardenability steel does not always equate to the optimal hardness, ductility and part compressive surface stress state.  The part designer must work with both the steel maker and the heat treater to optimize all three dimensions of hardened part properties.

Again, heat treating considerations must become part of the design and engineering processes from their inception. Heat treaters must give their input for what material is best for the part application, considering not only the desired part fit and function, but the needed physical and mechanical properties.  If we are to minimize waste in post-heat treat operations to achieve proper fit and function, at the lowest overall cost of manufacture, we need to collaborate with all the parties in the part making value chain.

Heat treating equipment in most heat treating departments is the same basic designs as decades ago.   The sunk costs in equipment the heat treater often dictates what heat treat processes will be done to the parts with little or no regard to the effect heat treatment has on total overall cost of manufacture.  Since heat treatment costs are typically between 5% to 10% of the total part cost, demonstrated cost savings from innovative heat treatments alone are rarely enough to justify a change to a new type of processing equipment even if demonstrated to be clearly better.

However, if the total cost of heat treatment includes an examination of the waste created “upstream” and “downstream” of the heat treatment process, often a change in heat treat processes can be shown to have a much larger effect on lowering he overall cost of parts making while making a better part for the end-user.  Achieving a proper balance of hardness and ductility in the part can be enhanced by also achieving a higher compressive surface stress state after quenching.   Higher compressive residual stresses can significantly increase part performance or yield higher power density at nominal cost.   Regardless of part hardness, compressive residual surface stress will usually enhance part wear and fatigue performance.   But to enable the optimal intensive quench that gives compressive residual surface stresses requires the part designer to collaborate with the heat treater.

A faster quench cooling rate usually will provide higher hardness to a deeper level in the part for a given alloy of steel.   Most heat treat metallurgists believe the higher cooling rate also means more part distortion or a higher probability of part cracking.  So many parts are designed around higher alloy air hardening grades of steel to get lower distortion after quenching.  However even gas quenching can cause unacceptable distortion in thin parts with complex shapes.

[blocktext align=”right”]Modern heat treat process modeling and intensive quenching practices have shown that the relationship between the probability of part cracking and rate of quench cooling is a bell curve. [/blocktext]

Modern heat treat process modeling and intensive quenching practices have shown that the relationship between the probability of part cracking and rate of quench cooling is a bell curve.  While it is true at very low cooling rates, such as gas quenching and molten salt quenching, there is a very low probability of part cracking, we also now know that at very high cooling rates which are uniformly applied to the part shell from the very beginning of the quench, the probability of part cracking is also very low.   The key is to eliminate the non-uniformity part cooling caused by film boiling at the very beginning of the quench process.

The benefit of “uniform + intensive” quench cooling is predictable part distortion and optimal grain refinement for a given alloy of steel.  In addition, intensive quench cooling develops “current” compressive surface stresses that hold the part like a die.  Even after tempering, high residual compressive surface stresses remain when designed into the part with the proper material alloy selection and the proper uniform and intensive quench process make for better parts at a total lower cost.   An added benefit is the elimination of the oil quenchants for increased safety, decreased environmental impact and cleaner parts without washing.

CONCLUSION:        

As heat treaters today, we must find the optimal processes and apply them in the best available equipment that eliminates the pains of heat treating from distortion and non-uniform properties for not only our customers, but our customers’ customer.  Obviously, we heat treaters cannot do this in a vacuum.  (Pun intended!)  Heat treating is integral and crosscutting with many different process technologies in the part making value stream.

For the heat treating industry to achieve the goals set forth for us so long ago, we must collaborate with all the other members in the part making value chain to optimize the heat treating processes we have always used and in some cases find new ways.  The simple fact is everyone at each step of part design and manufacture must collaborate to eliminate waste for the benefit of all in the lean value stream.  The order of processing is also very important.  To get it all right, the part making value map cannot be done from the individual silos of expertise.

Therefore, the selection of the optimal heat treatment process for a better part at a lower overall cost of manufacture is only enabled by a collaboration of the part designers, material makers and manufacturing engineers all working with their heat treater.

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